Charging device applied for making electrophotography

ABSTRACT

Disclosed herein is a charging device for use in electrophotography, characterized by a pair of corona charging devices facing each other with a suitable intervening space permitting the passage of photosensitive paper. Each corona charging device is provided with an auxiliary electrode, and at least one corona wire disposed in a holding space of the auxiliary electrode. High DC voltages of opposite polarities are applied respectively to the corona wires, and about 400 v. of AC voltage, which has been synchronized with the ripple voltages, of the high DC voltage is applied to the auxiliary electrodes. Consequently, the loss of the high DC voltage power source is reduced and a smaller power source can be applied for the charging device. Moreover, a very uniform corona discharge can be produced over a substantial portion of the entire charging period to attain a high speed charging.

United States Patent 50 Field ors i mii...,..

[54] CHARGING DEVICE APPLIED FOR MAKING ELECTROPHOTOGRAPHY 4 Claims, 2 Drawing Figs.

[52] U.S. Cl 250/495, 317/4, 317/262 [51] lnt.Cl H01j 37/26 2 5 0/49.5(60),

[56] References Cited UNITED STATES PATENTS 2,885,556 5/1959 Gundlach 250/49.5(61) 3,456,109 7/1969 Gawron 250/49.5(61) Primary Examiner-Archie R. Borchelt Assistant Examiner-C. M. Leedom Attorneys-Robert E. Burns and Emmanuel J. Lobato ABSTRACT: Disclosed herein is a charging device for use in electrophotography, characterized by a pair of corona charging devices facing each other with a suitable intervening space permitting the passage of photosensitive paper. Each corona charging device is provided with an auxiliary electrode, and at least one corona wire disposed'in a holding space of the auxiliary electrode. High DC voltages of opposite polarities are applied respectively to the corona wires, and about 400 v. of AC voltage, which has been synchronized with the ripple voltages, of the high DC voltage is applied to the auxiliary electrodes. Consequently, the loss of the high DC voltage power source is reduced and a smaller power source can be applied for the charging device. Moreover, a very uniform corona discharge can be produced over a substantial portion of the entire charging period to attain a high speed charging.

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CHARGING DEVICE APPLIED FOR MAKING ELECTROPHOTOGRAPHY corona discharge produced from the corona wire of the charging device is uniform only during a particular time in the.

charging period, and consequently the corona discharge can not follow a high speed charging. Also, in a device in which the high DC voltage of a difierent polarity is applied to the auxiliary electrode of the charging device, in order to make the corona discharge uniform over the entire charging period, the corona current which flows into the auxiliary electrode is abnormally large, so that it is unavoidable that a large scale power source of high DC voltage must be applied to compensate for a loss in the charging treatment. Furthermore, in this conventional type of device the composition of the charging device becomes complicated and large, because of the insulation of the auxiliary electrode which applies the high DC voltage, and the loss of the direct current source causes vibration of the corona wires, and this results in the severing of such wires.

The principal object of the present invention is to provide a double corona charging device eliminating the above-mentioned drawbacks of the conventional charging device applied for making electrophotography.

Another object of the present invention is to provide a double corona charging device applied for making electrophotography, further characterized by reducing the loss of the high DC voltage and applying a small scale power source.

A further object of the present invention is to provide a compact double corona charging device applied for making,

electrophotography, having very simple composition, with insulation means. k

A still further object of the present invention is to provide a double corona charging device applied for making electrophotography, characterized by a uniform corona discharge, approximately over the entire charging period, for providing high speed charging. I

Further features and advantages of the present invention will be apparent from the ensuing description, reference .being made to the accompanying drawings wherein:

' FIG. 1 is an explanatory circuit diagram of a double corona charging device according to the present invention,

FIG. 2 is an explanatory operation diagram of the double corona charging device shown in FIG. 1.

Generally, in the charging device of the, present invention, high DC voltages of different polarities are applied respectively, to corona wires of a pair of corona charging devices facing each other, and furthermore, about 400 v. of AC voltage which has been synchronized with the ripple voltage of the high DC voltage is applied to the auxiliary electrode of each corona charging device. Consequently, the loss of the high DC voltage power source is reduced and a smaller power source can be applied for the charging device. Moreover, since only about 400 v. of AC voltage is applied to the auxiliary electrode, said electrode can be insulated rather simply, and a uniform corona discharge is produced from the corona wire or wires approximately over the entire charging period to attain the high speed charging.

Referring to FIG. 1, an embodiment of the double corona charging device of the present invention comprises a pair of corona charging devices 1 and 4 facing each other. A plurality of corona wires 3 and 6 are enclosed in the respective holding spaces of the corona charging devices I and 4. The corona charging device I is provided with an auxiliary electrode 2 while the corona charging device 4 is provided'with an auxiliary electrode Sin such a way that the opened portions of the corona charginghdevices l and 4 face each other? In the abovementioned device, the negative high voltage is applied to the corona wires 3 while the positive high voltage is applied to the corona wires 6, and 400 v. of AC volta e, which has been synchronized with the ripple voltage of t e high voltage applied to the corona wires, is applied to the auxiliary electrodes Zand 5. v

Referring to FIG. 2, the wave forms applied to the corona wires 3 and 6 and auxiliary electrodes 2 and 5 by the voltage doubler high voltage power source are shown, wherein the positive and negative high voltages are 4.5 kv. each and the ripple percentage is 20 percent.

In the above-mentioned charging device, the potential difference between the positive or negativecorona wires and the respective auxiliary electrode becomes almost constant in a period, except the period indicated by the hatched area in FlG. 2 wherein the potential difference between the positive or negative corona wires and the respective auxiliary electrode becomes the minimum. Consequently, a uniform corona is emitted from each corona wire. in other words, as the period in which the corona discharge becomes irregular is negligibly small, a uniform electric charge can be imparted to the photosensitive layer 8 facing the negative corona charging device 1 by means of passing the photosensitive paper 7 through a space between the corona charging devices I and 4 at a high speed, for example 20 cm/sec.

As described above, in spite of using a small DC power source having a ripple percentage of 20 percent, the uniform corona discharge can be produced approximately over the entire charging period by applying 400 v. of AC voltage to the auxiliary electrodes 2 and 5, and the high speed charging can be operated by the charging device of the present invention.

While the invention has been described in conjunction with certain embodiments thereof, various changes and modifications may be made without departing from the scope and spirit of the present invention.

We claim: i

l. A charging device for use in electrophotography comprising a pair of corona charging devices facing each other, each corona charging device including an auxiliary electrode having a holding space, and each holding space having a corona wire disposed therein, means for applying a positive DC voltage to said corona wire of one of said corona charging devices, means for applying a negative DC voltage to said corona wire of the other corona charging device, and means for applying an AC voltage to said auxiliary electrodes, said AC voltage being in synchronization with inherent ripple voltages of the DC voltages. l

w 2. A charging device for use in electrophotography according to claim 1, wherein each corona charging device is provided with a plurality of corona wires disposed in a parallel configuration.

3. A charging device for use in electrophotography according to claim 1, wherein said means for applying an AC voltage comprises means for applying an AC voltage in the order of 400 v.

4. A charging device for use in electrophotography according to claim 1 wherein said corona charging devices are disposed with a suitable intervening space for spacing therebetween a photosensitive paper to be uniformly charged by the coronadischarge emitted from said corona wires, as said paper passes through said space. 

1. A charging device for use in electrophotography comprising a pair of corona charging devices facing each other, each corona charging device including an auxiliary electrode having a holding space, and each holding space having a corona wire disposed therein, means for applying a positive DC voltage to said corona wire of one of said corona charging devices, means for applying a negative DC voltage to said corona wire of the other corona charging device, and means for applying an AC voltage to said auxiliary electrodes, said AC voltage being in synchronization with inherent rIpple voltages of the DC voltages.
 2. A charging device for use in electrophotography according to claim 1, wherein each corona charging device is provided with a plurality of corona wires disposed in a parallel configuration.
 3. A charging device for use in electrophotography according to claim 1, wherein said means for applying an AC voltage comprises means for applying an AC voltage in the order of 400 v.
 4. A charging device for use in electrophotography according to claim 1 wherein said corona charging devices are disposed with a suitable intervening space for spacing therebetween a photosensitive paper to be uniformly charged by the corona discharge emitted from said corona wires, as said paper passes through said space. 